Compressed-air apparatus



(No Model.)

B. THOMSUN. COMPRESSED AIRAPPARATUS. No. 495,071. Patented Apr. 11. 1893,

Fnsl- W TPIESSEE UNITED STATES PATENT OFFICE.

ELIHU THOMSON, OF SWVAMPSCOTT, MASSACHUSETTS, ASSIGNOR TO THE THOMSON-HOUSTON ELECTRIC COMPANY, OF CONNECTICUT.

COMPRESSED-AIR APPARATUS.

SPECIFICATION forming part of Letters Patent No. 495,071, dated April 11, 1893. Application filed July 11, 1891. Serial No. 399,239- (No model.)

To all whom it may concern.-

Be it known that I, ELIHU THOMSON, of Swampscott, in the county of Essex and State of Massachusetts, have invented a certain new and useful Improvement in Compressed- Air Apparatus, of which th following is a specification.

This case relates to an invention in which the heating effect of an electric current is employed to assist the expansibility of compressed air before it is allowed to expand, as in the operation of drills and such like machines. It is well known that in expanding from the normal temperatures air becomes exceedingly cool and its effectiveness as a motive agency is very greatly reduced, and it is also Well known that by heating the air before it goes to the motive device (which allows it to expand) it maybe worked with great eihciency.

I also provide in my invention means for simultaneously controlling the application of current of the heating arrangement for the air at the same time that it is controlled in its application to the motive device or drill, so that it is not easily possible to cause destruction of the electric heating apparatus by cutting off the stream of air without cutting off the current to the heater.

In the accompanying drawings, Figure 1 shows the manner of application of the heating device and electrical supply circuit to a rock drill. Fig. 2 is a longitudinal section of the heater in the supply pipe. Fig. 3 shows a detail, and Figs. 4, 5, G, and 7 show modifications.

As shown in Fig. 1, a dynamo D supplies the line a I), while the compressed air pipe P supplies air to the drill, as at D, set in motion by such air under pressure. A valve V of the compressed air supply pipe is arranged to be operated simultaneously with a switch S in the supply circuit a b for the heater K. The device is not, however, limited to any special arrangement of the switch, as the switch S might be a shunt switch in series circuit diverting the current from the device K instead of opening the circuit through it.

The heater which is inserted in the supply pipe consists of the chamber K, and a heating resistance R contained therein and connected with the supply circuit a b. The chamber K, is lined preferably with insulating material K such as asbestus or mica having the power of resisting heat.

The Valve V for controlling the admission of compressed air through the apparatus is arranged as described to operate simultaneously the switch S so that the whole stream is out off when the current is cut off, and the whole strength is let on when the current is let on. The resistance R R is made of such amount in proportion to the current flowing as to generate considerable heat during the passage of the current and communicates heat to the air stream flowing through it or adjacent to it. The resistance may be protected by a fuse F removably secured by nut N.

The fuse proper may be made as a fusible tip to a bar of comparatively infusible metal F, as seen in Fig. 3.

Where the currents which are to be fed to the apparatus are of so small Volume and such high potential that the resistance to obtain the heat would be a very fine structure of very high resistance and not easily constructed, I prefer to employ the principle of induction as exemplified in Fig. 4, where a b may be the mains carrying alternating currents. These currents are passed by the controlling action of a switch S, through the primary coil G wound upon the iron core I alongside of the heavy secondary conductor H, whose terminals are connected to the ends of the section of pipe K which forms the heating resistance. It is ordinarily of much higher resistance relatively than the secondaryll II and it may be insulated or not from the rest of the pipe P P carrying compressed air. The passage of the current in the primary generates currents which heat the section of pipe K in the secondary and heats the air stream passing through it.

In Figs. 4, 5, and 6, the secondary H itself is made hollow or is a convolution of pipe forming a closed electric circuit.

Fig. 7 shows the resistanceR (Fig. 2) made by packing wire gauze in layers within the chamber of pipe K, whereby a very great surface is obtained, and sufficient resistance when the currents are of considerable volume.

What I claim as new, and desire to secure by Letters Patent, is-

1. The combination with a compressed air motive device, an electric heater arranged in heating relation to the air supplied to said device, a valve for cutting on? said air supply and a switch connected to said valve and controlling the supply circuit of said electric heater.

2. The combination of the compressed air motive device, the air supply pipe therefor, the heating resistance arranged in heating relation to the air in said pipe and in circuit with a source of current supply, the valve controlling the fiow of air in said pipe, and the switch operatively connected to said valve and controlling the supply of electric current to the resistance.

3. The combination with a closed air-containing chamber having an imperforated metallic casing of a transformer having its secondary circuit closed through said casing and its primary in connection with an alternating current source.

4. The combination of the closed air supply pipe of conducting but resistant material, of the transformer having its secondary in circuit with a portion of said supply pipe and its primary in connection with an alternating current source.

In witness whereof I have hereunto set my hand this 8th day of July, 1891.

ELIHU THOMSON.

Witnesses:

JOHN W. GIBBONEY, JOHN T. BRODERICK. 

